Connector assembly for a circuit board testing machine, a circuit board testing machine, and a method of testing a circuit board by means of a circuit board testing machine

ABSTRACT

A machine for testing a circuit board of an electrically insulating material includes circuit tracks of an electrically conductive material arranged on one or opposite side surfaces. At least one test surface is provided. The test surface or each of them defines a number of test points electrically insulated relative to one another and arranged in a matrix configuration. For establishing electrically conductive connection between selected test points of the test surface and selected areas, e.g. circuit tracks of the circuit board to be tested, a connector assembly is sandwiched between the one side surface of the circuit board to be tested and the test surface. The connector assembly is a double-sided circuit board having individual connectors arranged on first and second side surfaces of the circuit board and connected through conductors extending through the circuit board in a configuration corresponding to the selected areas of the circuit board to be tested and the selected points of the test surface, respectively.

This is a division of copending application Ser. No. 770,867, filed Aug.12, 1985 now U.S. Pat. No. 4,707,657.

The present invention relates to a connector assembly for a circuitboard testing machine.

Hitherto a visual inspection or examination of circuit boards,especially printed circuit boards, has been a sufficient "testing"routine as to the correctness of single-sided or double-sided printedcircuit boards. However, the appearance of more complex, more compact,more elaborated, and consequently more expensive circuit boards, such asthin-film or thick-film circuit boards, i.e. circuit boards includingcircuit tracks provided in thin-film or thick-film technique,respectively, multi-layer printed circuit boads, i.e. printed circuitboards including several layers of boards made of an insulating materialhaving circuit tracks of an electrically conductive material arranged onone side surface of each of the boards and further through-platingsconnecting the circuit tracks of the individual boards to one another,and circuit boards combining the printed circuit board technique, themulti-layer printed circuit board and layer techniques, e.g. theso-called mixed boards or boards provided in PTF technique (PTF: PolymerThick-Film), requires a more accurate and reliable testing routine, as avisual inspection or examination may not reveal an incorrectness of thecircuit board, especially an incorrectness of a multi-layer circuitboard having incorrect circuit connections embedded within the circuitboard assembly. An incorrectness of a thin-film or thick-film circuitboard may also be hard to detect by visual inspection, even when amicroscope is employed.

For providing a more reliable and economical testing routine than thevisual inspection or examination of a circuit board, i.e. a board madeof an insulating material having circuit tracks of an electricallyconductive material arranged on at least one side surface thereof, suchas a single-sided, double-sided or multi-layer printed circuit board, aceramic thick-film substrate or the like, circuit board testing machineshave been developed. These known testing machines are adapted to supplyDC or AC current to a selected point or area of the circuit tracks ofthe circuit board and to determine the current transferred to otherselected points or areas of the circuit tracks of the circuit board.These testing machines have been equipped or adapted to a particularcircuit board layout, as individual connector pins have been arranged ina configuration corresponding to the selected points or areas of thecircuit board layout in question and internally connected to currentgenerating means and current measuring means through switching means.The testing machines have further been programmed to the circuit boardlayout in question, and on the basis of the information programmed intothe testing machine, the machines are able to determine whether acircuit board includes the required circuit board connections and nofurther connections, and, consequently, whether the tested circuit boardis a correct circuit board, or whether the circuit board includeserroneous connections or fails to include certain connections, and,consequently, whether the test circuit board is an incorrect circuitboard. However, as the circuit board testing machine has to be equippedor adapted to the circuit board layout in question, the automaticcircuit board testing routine is only profitable in connection withlarge-scale production of circuit boards.

Furthermore, due to the individual connector pins, the prior art testingmachines are not able to test highly delicate and compact circuit boardssuch as thin-film or thick-film substrates, mixed boards or boardsprovided in PTF technique, and furthermore, they are not able to testcircuit boards having components mounted thereon. The connector pinconcept of the prior are testing machines also makes these machineshighly liable to mechanical failure.

Therefore, there is a need for a connector assembly for a circuit boardtesting machine, rendering the circuit board testing machine more easilyadaptable to different circuit board layouts, and, consequently,rendering it possible to perform machine tests of different circuitboards of different layouts, even of a relatively small number, and evencircuit boards of highly complex, compact and elaborated configuration,such as multi-layer printed circuit boards, circuit boards provided inPTF technique, mixed boards, or highly complicated thin-film orthick-film circuit boards and, furthermore, circuit boards havingcomponents mounted thereon.

This need is fulfilled by means of a connector assembly according to theinvention for a circuit board testing machine having a connectorassembly for a circuit board testing machine having a test surfaceincluding a number of test points electrically insulated relative to oneanother and arranged in a matrix configuration and for testing a circuitboard of an electrically insulating material having circuit tracks of anelectrically conductive material arranged on at least one side surfacethereof, the connector assembly being adapted to provide electricalconnection between selected areas of the circuit board and selected testpoints of the test surface of the testing machine, the connectorassembly comprising:

a board of an electrically insulating material having opposite first andsecond side surfaces,

a first plurality of individual connector means being arranged on thefirst side surface of the connector assembly board in a configurationcorresponding to said selected areas of the circuit board,

a second plurality of individual connector means being arranged on thesecond side surface of the connector assembly board in a configurationcorresponding to said selected test points of the testing machine, and

electrical conductor means extending through the connector assemblyboard and electrically connecting said individual connector means ofsaid first plurality to respective individual connector means of saidsecond plurality.

Normally, the electrical conductor means extend through holes of theconnector assembly. However, certain insulating materials may in atreatment be made electrically conductive, and the electrical conductormeans of the connector assembly may consequently be provided in aselective treatment of the insulating material of the board.

The connector assembly normally serves the purpose of providingelectrical connection between selected areas of the circuit tracks ofthe circuit board and selected test points of the test surface of thetest machine. However, certain circuit boards, e.g. circuit boards forHF (High Frequency) applications or circuit boards involving certainsecurity requirements such as requirements as to insulation betweenparticular circuit tracks, may advantageously be tested by providingelectrical connection by means of the connector assembly according tothe invention between one or more test points of the test surface andselected areas interposed the circuit tracks of the circuit board.Furthermore, the circuit board to be tested may have components arrangedthereon, e.g. discrete components, components provided in layertechnique, such as printed resistors, printed capacitors, and printedinductors or chip components.

The connector assembly may in a first embodiment provide directelectrical connection between selected areas of the circuit board andthe test points of the test surface through its individual connectormeans of the first and second pluralities and further through itselectrical conductor means. However, in the presently preferredembodiment of the invention, the connector assembly further comprises atleast one sheet of an electrically insulating material, arranged on oneside surface of the board of the connector assembly and havingthrough-going, electrically conductive paths. The sheet consequentlyserves the purpose of providing electrical connection through itsthrough-going, electrically conductive paths between the individualconnector means of the first plurality or the second plurality, arrangedon the first side surface and on the second side surface, respectively,of the board of the connector assembly and selected areas of the circuitboard and the selected test points of the testing machine, respectively.

The sheet is preferably of a highly insulating material, such as a sheetof a polymer material, and the through-going, electrically conductivepaths are preferably constituted by metal fibres of high electricalconductivity, of a thickness of 2-100 μm, preferably 5-30 μm, and of adensity of 1-20 fibres per mm². In order to reduce any corrosiveinfluence on the metal fibres, the metal firbres are preferably of anoble metal such as silver, platinum or, preferably, gold.

As mentioned above the sheet may be arranged on the first side surfaceof the board of the connector assembly or, alternatively, on the secondside surface of the board of the connector assembly. In the preferredembodiment of the invention, the connector assembly comprises a firstand a second sheet of the above type, i.e. of an electrically insulatingmaterial and having through-going, electrically conductive paths, thefirst sheet being arranged on the first side surface of the board of theconnector assembly, so as to establish electrical connection betweensaid selected areas of the circuit board and the first plurality ofindividual connector means, and the second sheet being arranged on thesecond side surface of the board of the connector assembly, so as toestablish electrical connection between said selected test points of thetesting machine and the second plurality of individual connector means.

The teachings of the present invention are applicable to printed circuitboard technique including single-sided, double-sided and multi-layerprinted circuit boards, mixed boards and circuit boards provided in PTFtechnique, as well as to thin-film or thick-film technique, and theconnector assembly according to the invention may be provided inaccordance with any of these techniques or any combination of thesetechniques.

Consequently, the board of the connector assembly may be constituted bya board of a double-sided printed circuit board, the first or secondplurality of individual connector means comprising printed circuit padsbeing arranged on a first side surface and on a second side surface,respectively, of the double-sided printed circuit board, and theconductor means of the connector assembly being constituted bythrough-platings of the double-sided printed circuit board, or the boardof the connector assembly may, alternatively, be constituted by athick-film or thin-film substrate, the first and second plurality ofindividual connector means comprising layers provided in thick-film orthin-film technique arranged on a first side surface and on a secondside surface, respectively, of the substrate. The board of thedouble-sided printed circuit board and the substrate may be a solidboard or substrate, respectively, or, alternatively, be constituted by aflexible sheet or foil, e.g. a polymer sheet.

It should be mentioned that the board of the connector assembly may beprovided in accordance with any of the above circuit board techniquesand be employed for testing a circuit board also provided in accordancewith any of these techniques.

As the circuit board to be tested is conventionally designed byemploying computer aided design technique (CAD-technique), the computerwhich actually designs the circuit board layout inherently knows thelayout of the circuit board and therefore only has to be programmed asto the matrix configuration of the test points of the circuit boardtesting machine in question for designing the configuration ofindividual connector means of the first and second pluralities and,consequently, for providing the connector assembly according to theinvention.

In order to make the testing machine discriminate between the differenttest areas of the circuit board to be tested, the number of individualconnector means of said second plurality is preferably identical to thatof said first plurality. Therefore, the conductor means of the connectorassembly provide a one-to-one correspondence between the individualconnector means arranged on the first side surface of the connectorassembly board and the individual connector means arranged on the secondside surface of the connector assembly board.

One of the main features of the connector assembly according to theinvention is that the connector assembly, as described above, may beprovided very easily involving double-sided printed circuit boardtechnique and employing relatively inexpensive materials, and in thepresently preferred embodiment of the connector assembly according tothe invention the board of the double-sided printed circuit board is aconventional 1.5 mm glass fibre reinforced epoxy resin board, and theprinted circuit pads are 25-100 μm Cu-layer pads, such as 35 μm or 70 μmCU-layer pads, preferably provided with gold platings.

In a further embodiment of the double-sided printed circuit boardembodiment of the connector assembly according to the invention, theindividual connector means of said first or second plurality may furthercomprise connector bodies of an electrically conductive material, as theconnector bodies increase the mechanical strength of the connectormeans.

In a further embodiment, the conductor bodies may be arranged inrespective bores of a supporting board of an electrically insulatingmaterial and aligned relative to their respective printed circuit pads.In this embodiment, the connector bodies may be solid bodies made of anelectrically conductive elastomer cooperating with a substantiallynon-compliant or inelastic supporting board. Alternatively, the supportboard may be of a compliant or elastic material, and/or the connectorbodies may be constituted by substantially inelastic bodies.

In an alternative embodiment of the double-sided printed circuit boardembodiment of the connector assembly according to the inventionincluding connector bodies, the connector bodies are solid, metallicbodies. The solid metallic bodies may be pins or alternatively male orfemale connectors adapted to cooperate with mating female or maleconnectors.

It is to be emphasized that the above described embodiments of theconnector assembly according to the invention may be combined, in thatthe individual connector means of one of the pluralities may be providedin accordance with any of the above embodiments of the connectorassembly, and the individual connector means of the other plurality maybe provided in accordance with any of the above embodiments of theconnector assembly according to the invention. Furthermore, thedifferent embodiments of the individual connector means may be combinedwithin one of the pluralities without departing from the concept of thepresent invention.

The present invention also relates to a testing machine for testing acircuit board of an electrically insulating material having circuittracks of an electrically conductive material arranged on at least afirst side surface thereof, and comprising a test surface including anumber of test points electrically insulated relative to each other andarranged in a matrix configuration and the connector assembly having anyof the above described characteristics of the connector assemblyaccording to the invention and adapted to be arranged on said first sidesurface of the circuit board providing electrical connection betweenselected areas of the first side surface of the circuit board andselected test points of the test surface through the individualconnector means of the connector assembly.

The circuit board testing machine is adapted to test the circuit boardfrom the first side surface thereof. The circuit board testing machineaccording to the invention may alternatively or further be adapted totest a circuit board further having circuit tracks arranged on thesecond side surface opposite to said first side surface, i.e. to test adouble-sided printed circuit board, a multi-layer printed circuit board,a circuit board provided in thin-film or thick-film technique havingthin-film or thick-film layers, respectively, arranged on both sidesurfaces of the substrate of the circuit board, or a circuit boardprovided in PTF technique, or a mixed board having circuit tracksarranged on both side surfaces, and in its presently preferredembodiment the circuit board testing machine comprises two opposite testsurfaces for receiving the circuit board therebetween and two connectorassemblies having any of the above characteristics of the connectorassembly according to the invention and adapted to be arranged onopposite side surfaces of the circuit board.

For testing a circuit board further having circuit tracks arranged on asecond side surface opposite to said first side surface, the circuitboard testing machine according to the invention may alternativelyfurther comprise a short-circuiting board and a further connectorassembly having any of the above characteristics of the connectorassembly according to the invention and adapted to be arranged on saidsecond side surface of the circuit board for providing electricalconnection between selected areas of the second side surface of thecircuit board and selected areas of the short-circuiting board.

The circuit board testing machine according to the invention may beadapted to test the circuit board by manual connection of a generatormeans to one or more test points of the testing machine and by detectionor measurement of the signal transmission to other test points of thetesting machine. Thus, the signal generator means are external means andan external signal measuring means is further employed. In an automaticcircuit board testing machine according to the invention, the machinefurther comprises first means for generating a test signal, second meansfor supplying a test signal to the test points individually, third meansfor addressing the test points individually and for receiving a signaltherefrom, and fourth means for measuring the signal received from thethird means. Furthermore the circuit board testing machine may comprisecontrol means for controlling the overall operation of the machine, suchas a microprocessor controller means, and may further or alternativelybe connected to external control or processing means such as an externalcomputer which may further control an automatic production of circuitboards involving testing of the individual circuit boards by means ofthe circuit board testing machine according to the invention.

The present invention further relates to a method of testing a circuitboard by means of a circuit board testing machine having a test surfaceincluding a number of test points electrically insulated relative toeach other and arranged in a matrix configuration and for testing acircuit board of an electrically insulated material having circuittracks of an electrically conducting material arranged on at least afirst side surface thereof, the method comprising:

arranging said first side surface of the circuit board facing the testsurface of the testing machine and sandwiching a connector assemblyhaving any of the characteristics of the above described connectorassembly according to the invention therebetween for providingelectrical connection between selected areas of the first side surfaceof the circuit board and selected test points of the test surface of thetesting machine through the individual connector means of the connectorassembly.

If the circuit board further has circuit tracks arranged on a secondside surface opposite to said first side surface, the method accordingto the invention may in a first embodiment further comprise employing acircuit board testing machine having a further test surface opposite tosaid at least one test surface and arranging the second side surface ofthe circuit board facing the further test surface of the testing machineand sandwiching a further connector assembly having any of thecharacteristics of the above described connector assembly according tothe invention therebetween for providing electrical connection betweenselected areas of the second side surface of the circuit board andselected test points of the further test surface of the testing machinethrough the individual connector means of the further connectorassembly, or, alternatively, in a second embodiment further comprisesarranging a short-circuiting circuit board facing the second sidesurface of the circuit board sandwiching a further connector assemblyhaving any of the characteristics of the above described connectorassembly according to the invention therebetween for electricallyinterconnecting selected areas of the second side surface of the circuitboard.

Normally, the selected areas of the circuit board constitute selectedareas of the circuit tracks of the circuit board in order to positivelytest the electrical conductive circuit track or circuit pattern of thecircuit board. Consequently, in accordance with a further embodiment ofthe method according to the invention at least one of the said selectedareas may constitute a selected area of the circuit tracks of thecircuit board. However, as mentioned above, certain circuit boards, e.g.circuit boards for HF (High Frequency) applications or circuit boardsinvolving certain security requirements such as requirements as toinsulation between particular circuit tracks may advantageously betested by providing electrical connection to a selected area interposedthe circuit tracks of the circuit board in order to render possible thetest or measurement of the insulation between the circuit tracks inquestion or the capacitive or inductive coupling therebetween.Consequently, in accordance with a further or alternative embodiment ofthe method according to the invention at least one of the said selectedareas may constitute a selected area interposed selected circuit tracksof the circuit board.

The invention will now be further described with reference to thedrawings, wherein

FIG. 1 is a vertical, sectional view through a top surface of a circuitboard testing machine, a connector assembly according to the inventionand a circuit board to be tested,

FIG. 2 is a vertical, sectional view through a second embodiment of aconnector assembly according to the invention,

FIG. 3 is a vertical, sectional view through a third embodiment of aconnector assembly according to the invention,

FIG. 4 is a vertical, sectional view through a fourth embodiment of aconnector assembly according to the invention,

FIG. 5 is a vertical, sectional view through a fifth embodiment of aconnector assembly according to the invention,

FIG. 6 is a vertical, sectional view through a sixth embodiment of aconnector assembly according to the invention,

FIG. 7 is an overall perspective view of a circuit board testing machineaccording to the invention,

FIG. 8 is a perspective and partially broken away view of a test headconstituting a component of the circuit board testing machine shown inFIG. 7 and including a test surface of the circuit board testingmachine,

FIG. 9 is an exploded and perspective view of two test heads includingtwo test surfaces and constituting two individual components of thecircuit board testing machine shown in FIG. 7, and illustrating theconcept of sandwiching a circuit board to be tested between twoconnector assemblies according to the invention which are furthersandwiched between the test heads of the circuit board testing machine,

FIG. 10 a vertical sectional view basically through the test head,connector assembly and circuit board set up of FIG. 9, in which one ofthe test heads is replaced by a short-circuiting or dummy circuit board,

FIG. 11 is a diagram illustrating the matrix addressing of the testpoints of the test surface of the test head shown in FIGS. 8 and 9, and

FIG. 12 is an overall schematical view of the circuit board testingmachine shown in FIG. 7 connected to an external control computer andfurther illustrating the internal microprocessor of the testing machine.

In FIG. 1, a schematical, vertical, sectional view through a firstembodiment of a connector assembly 10 according to the invention isshown. The connector assembly 10 comprises an assembly board 12 of aninsulating material, such as a 1.5 mm glass fibre reinforced epoxy resinboard, having printed circuit pads 14 and 16 arranged on the top surfaceand on the bottom surface, respectively, of the assembly board 12. Theprinted circuit pads 14 and 16 are made of 35 μm or 70 μm Cu-layersprovided with gold platings, and each of the top surface printed circuitpads, such as the pad designated 14, is connected to a respective bottomsurface, printed circuit pad, such as the pad designated 16 through ametallic conductor 18 constituted by a through-plating of thedouble-sided printed circuit board or connector assembly 10. The topsurface printed circuit pads and the bottom surface printed circuitpads, such as the pads 14 and 16, respectively, are each provided withan electrically conductive connector body, such as the bodies designated20 and 22, respectively, constituted by electrically conductiveelastomeric bodies.

The connector assembly 10 is adapted to cooperate with a circuit boardtesting machine such as a manual testing machine or an automatic testingmachine, a modified, conventional circuit board testing machine or,preferably, a circuit board testing machine according to the inventionto be described below. The upper side surface part of the circuit boardtesting machine shown in FIG. 1 and designated the reference numeral 24is provided with a number of test point pads, one of which is designatedthe reference numeral 26, and which are arranged in spaced apart,insulated relationship in a matrix configuration together constituting atest surface. Thus, the distance between two adjacent test point pads ise.g. 1/10" (2,54 mm) or 2.5 mm. The test point pads are internallyconnected to switching means of the circuit board testing machine forconnecting a test point pad to a current generator means or to a currentdetector means in order to carry out a circuit board testing routine aswill be described below.

The connector assembly 10 is further adapted to cooperate with a circuitboard to be tested and comprising a circuit board 28 of an insulatingmaterial, such as a conventional, printed circuit board having printedcircuit tracks arranged on at least one side surface thereof, such asthe printed circuit tracks or pads arranged on the lower side surface ofthe printed circuit board 28, one of which is designated the referencenumeral 30. The printed circuit board 28 is a bare board, i.e. a boardwithout any components mounted thereon, however, the circuit board mayalternatively be provided with electronic components. Furthermore, theconnector assembly 10 according to the invention may alternatively beemployed for testing other circuit boards, such as thick-film orthin-film substrates having conductive layers applied on a single orboth side surfaces of the substrate, multi-layer printed circuit boards,mixed boards, circuit boards provided in PTF technique or anycombination of these circuit boards further provided with components ifdesired.

The layout of the circuit board to be tested, i.e. the layout of theprinted circuit board 28, is determined solely by the layout of theelectronic circuitry to be provided by the electronic component to bemounted on the circuit board. Therefore, the arrangement of the printedcircuit pads 14 arranged on the top surface of the connector assembly 10is determined by the arrangement of the printed circuit tracks orprinted circuit pads arranged on the lower side surface of the printedcircuit board 28. Normally, the printed circuit pads 14 are arrangedaligned in relation to a printed circuit track or printed circuit pad ofthe printed circuit board 28 so as to establish electrical contact tothe printed circuit track or the printed circuit pad in question.

However, certain circuit boards, such as circuit boards for HF (HighFrequency) applications and circuit boards involving securityrequirements, e.g. requirements as to insulation between circuit tracksor circuit pads, are preferably tested by providing a printed circuitpad 14 at a position interposed in relation to the printed circuittracks or printed circuit pads of the circuit board so as to renderpossible the detection of irregularities of the insulating area betweenthe printed circuit pads or printed circuit tracks in question. Suchirregularities may originate from insufficient etsing of the printedcircuit board. In connection with substrates having layers applied on asingle or both side surfaces of the substrate, there is a pronouncedrisk that the layers constituting the conductive circuit tracks orcircuit pads of the circuit board become mashed or smeared due todeficiencies in the production process. Obviously, deficiencies of theinsulation between circuit tracks or circuit pads of the circuit boardmay have different origin in thin-film or thick-film, multi-layer,printed circuit, etc. techniques.

Contrary to the printed circuit pads 14, the arrangement of the printedcircuit pads 16 arranged on the lower side surface of the connectorassembly 10, is determined by, on the one hand, the respective upperside surface printed circuit pad 14 and, on the other hand, thenearest-by test point pad 26 of the test point pad matrix configurationof the test surface of the circuit board testing machine. As manycircuit boards are designed by employing computer aided design (CAD-)technique, the computer which designs the circuit board, is very easilyprogrammed to further design the connector assembly 10 or the basicdouble-sided printed circuit board 12 thereof, as the computer is onlyto be programmed to design a double-sided printed circuit board, oneside of which is determined solely by the layout of the printed circuitboard 28 and the other side of which is to reveal a fixed distanceconnector body configuration corresponding to the matrix configurationof the test point pads 26.

As mentioned above, the circuit board assembly 10 according to theinvention may be employed for testing any circuit board, such assingle-sided or double-sided printed circuit boards, multi-layer printedcircuit boards, mixed circuit boards, circuit boards provided inthick-film or thin-film technique or in PTF technique or any combinationof the these techniques. Furthermore the connector assembly 10 accordingto the invention may be provided in accordance with any of thesetechniques in order to fulfill any specific requirements, such asrequirements as to rigidity, flexibility or strength of the connectorassembly 10 and further any production concerned. Normally a printedcircuit board, such as a single-sided, a double-sided or a multilayerprinted circuit board is tested by employing a connector assembly 10according to the invention provided in printed circuit board technique.Similarly, a circuit board provided in layer or film technique may betested by employing a connector assembly also provided in accordancewith the film technique in question. However, the production techniquemay be combined in that a connector assembly 10 provided in for exampleprinted circuit board technique, may be employed for testing athick-film substrate or vice versa. However, in order to provide afairly cheap, yet accurate connector assembly, the printed circuit boardtechnique is preferably employed for most testing applications, such asthe testing of printed circuit boards, thick-film substrates, mixedcircuit boards or circuit boards provided in PTF technique.

As is conventional in the art and will be described below in greaterdetail with reference to FIG. 11, the actual test routine is carried outby supplying DC or AC current to the individual test point pads 26 oneat a time, and by detecting the current transfer to any other test pointpad of the test surface. As will be evident, the test point pads 26 areconnected individually through the connector bodies 22, the lower sideprinted circuit pads 16, the through-platings 18, the top surface,printed circuit pad 14 and the connector bodies 20 to a respectiveprinted circuit pad or part of a printed circuit track 30 of the printedcircuit board 28 to be tested.

In FIG. 2, an alternative or second embodiment of the connector assembly10 according to the invention is shown. Apart from the above describedcomponents, the assembly board 12, the printed circuit pads 14 and 16and the through-plating 18, the connector assembly comprises an upperside surface board 32 and a lower side surface board 34 of an insulatingmaterial, such as the material of the assembly board 12, e.g. glassfibre reinforced epoxy. In cylindrical bores of the supporting boards,electrically conductive, spherical connector bodies 36 and 38, arearranged. The spherical connector bodies 36 and 38 are press-fitted intothe respective bores of the respective boards, which maintain themaligned relative to the printed circuit pads 14 and 16, respectively.

In FIGS. 3 and 4, a third and a fourth embodiment of the connectorassembly according to the invention is shown, basically identical to theembodiment of the connector assembly shown in FIG. 2, however, differingtherefrom in that the electrically conductive, spherical connectorbodies 36 and 38 are substituted by electrically conductive, cylindricalor cubic bodies 40 and 42, respectively, shown in FIG. 3 andelectrically conductive, cylindrical bodies 44 and 46, respectively,shown in FIG. 4, having outwardly domed surfaces. Furthermore, in FIG.3, the upper side surface board 32 and the lower side surface board 34,shown in FIGS. 2 and 4, which are substantially non-compliant orinelastic supporting boards, are replaced by compliant or elastic upperside surface and lower side surface boards designated 33 and 35,respectively.

The bodies 36 and 38 of FIG. 2, the bodies 40 and 42 of FIG. 3, and thebodies 44 and 46 of FIG. 4 may be constituted by conduction elastomericbodies, such as bodies provided from the material Consil® --E, --II,--R, --C, or SC-Consil® from the company Tecknit®, EMI ShieldingProducts. Alternatively, the bodies 36, 38, 40, 42, 44, 46 may beconstituted by bodies of wire mesh resilient contact elements of thetype Fuzz Button® of the above company.

In FIG. 5, a fifth and presently preferred embodiment of the connectorassembly 10 according to the invention is shown. In this embodiment ofthe invention, the above printed circuit pads 14 and 16 are substitutedby printed circuit pads or printed circuit tracks 48 and 50,respectively, of an outwardly domed configuration. It should bementioned that the printed circuit tracks 48 and 50 of the presentlypreferred embodiment of the connector assembly 10 according to theinvention render it possible to test the circuit boards not only atspecific points determined by the positions of the circuit pads but alsoat more spacious areas such as at insulating areas between circuittracks or circuit pads of the circuit board. On the upper side surfaceand on the lower side surface of the assembly board 12, an upper sidesurface sheet 52 and a lower side surface sheet 54, respectively, arearranged, the sheets being made of an electrically insulating materialin which through-going electrically conductive paths are embedded. Thesheet material has been supplied from the company CHOMERICS®, under thename CHO-NECTOR®, described in Technical Bulletin No. 972, and furtherfrom the company Shin-Etsu Polymer Co., Ltd., under the name of ShinetsuInterconnector "MAF" type.

In FIG. 6 a sixth embodiment of the connector assembly according to theinvention is shown. The embodiment shown in FIG. 6 is a furtherembodiment of the above described embodiments shown in FIGS. 2-4 andcomprises, apart from the assembly board 12, the printed circuit pads 14and 16 and the through-plating 18, an upper side surface board 56 and alower side surface board 58 of an insulating material. In through-goingbores of the boards 56 and 58, two connector means are arranged inelectrically conductive connection with the printed circuit pads 14 and16. The connector means of the upper side surface board 56 comprises asolid, metallic body 60 and a coil 62 biassing the body 60 outwardly orupwards, and the connector means of the lower side surface board 58comprises a solid, metallic body 64 and a coil 66 biassing the body 64outwardly or downwards.

In FIG. 7, a circuit board testing machine according to the invention isshown designated 70 in its entirety. The circuit board testing machinecomprises a base frame 72 to the lower side surface of which four feet74 are secured. The machine 70 further comprises a housing 76 in which afront recess 78 is provided. The machine 70 is a mains operated electricor electronic apparatus and on the front surface of the housing,operator operable switches 80 and 81 are arranged next to a display 82which serves the purpose of displaying information to the operatorregarding the testing of a circuit board and the state of the apparatus.

In the front recess 78, a first and a second test surface, or an upperand a lower test surface of the testing machine are defined. In FIG. 7,only the second or lower test surface is shown and designated 84. Theupper and lower test surfaces of the testing machine 70 are identical toeach other and defined on an outer side surface of a test head shown inFIG. 8 which constitutes a component of the circuit board testingmachine 70. Ihe lower test surface 84 and also the upper test surfacenot shown in FIG. 7 comprise a number of test points electricallyinsulated relative to one another and arranged in a matrixconfiguration. In the embodiment of the testing machine 70 shown in FIG.7 and of the test head of the testing machine shown in FIG. 8, a testpoint matrix of 16×16 is defined. The test surfaces or at least one ofthe test surfaces are mounted so as to reciprocate to and from theopposite test surface by means of one or more motors generating thereciprocating motion or motions of the test surface or the testsurfaces, respectively. The motor or motors may be constituted by anyappropriate motor device, such as an electromagnetic motor, e.g. anelectromotor or a solenoid motor, a device operated by compressed air orby a pressurized fluid, e.g. a hydraulic device. In the embodiment ofthe circuit board testing machine shown in FIG. 7, only the upper testsurface of the testing machine is movable by means of a motor which isshown in dashed lines and is constituted by a solenoid motor 86.

In FIG. 8, one of the test heads of the circuit board testing machine 70of the present invention is shown. The test head is designated thereference numeral 100 and is basically a circuit board assemblycomprising a top circuit board 102, a base circuit board 104 and aplurality of circuit boards 106 interconnecting the top circuit board102 and the base circuit board 104. As evident from FIG. 8, theplurality of circuit boards 106 constitutes a total of sixteen circuitboards corresponding to the dimension of the test point matrix 16×16.The outer, or lower as shown in FIG. 8, side surface of the base circuitboard 104 constitutes the test surface 84 of the test head andconsequently one of the test surfaces of the circuit board testingmachine. Each point of the test surface is connected to one of thecircuit boards 106. The circuit boards 106 define an X-co-ordinate ofthe test points of the test surface, and on each of the circuit boards106 an Y-coordinate of the individual test point of the test surface isfurther defined. Any test point of the test surface may consequently bedefined by a set of co-ordinates (X,Y).

The base circuit board 104 as well as the top circuit board 102 and thecircuit boards 106 are double-sided printed circuit boards. The testpoints of the test surface 84 are consequently constituted by individualCu-layer pads of a thickness of 35 μm or 70 μm, further provided withgold platings. Through a through-plating each test point of the testsurface, i.e. each circuit pad on the lwoer or outer side surface of thebase circuit board 104 is connected to a terminal 108 on the upper sidesurface of the base circuit board 104. The circuit boards 106 haveconnector terminals one of which is designated the reference numeral 110and which are soldered to the terminals 108 of the base circuit board104 in order to provide electrically conductive connection between theconnector terminals 110 of the circuit boards 106 and respective testpoints of the test surface 84.

Through addressing or switching transistors, one of which is designatedthe reference numeral 112 and of a configuration to be described belowwith reference to FIG. 11, the terminals 110 are connected to furtherconnector terminals, one of which is designated the reference numeral114 of the circuit boards 106.

The terminals 114 are received in soldered connections of the topcircuit board 102 and through printed circuit tracks connected tomulti-pin plugs 116 which, as is evident from FIG. 8, comprises a totalof sixteen pins each. On the top circuit board 102, a total of fourmulti-pin plugs 116 are provided. Consequently, the 16×16 matrix of thetest points of the test surface are addressable through four sixteen pinplugs 116.

In addition to the connector terminals 110 and 114 and the internalcircuit tracks of the circuit board, the circuit boards 106 areinterconnected through solid rod connectors, one of which is designatedthe reference numeral 118 which extend through through-going holes ofthe circuit boards 106. Evidently, the test head may be modified into atest head of a different matrix configuration, e.g. into a test headcomprising a 24×24 matrix test point configuration or a 32×32 or anyother matrix test point configuration.

FIG. 9 shows an exploded view of the test heads 100, one of which wasshown in FIG. 8, of the circuit board testing machine 70 shown in

FIG. 7 according to the invention, and further of two connectorassemblies according to the invention and a circuit board to be tested.In the top of FIG. 9, a first or top test head is shown defining a testsurface 84 facing downwardly. Below the downwardly facing test surfaceof the test head 100, a connector assembly of the type described abovewith reference to FIG. 5 is shown comprising a double-sided printedcrircuit board 120, a first sheet 122 and a second sheet 124 of theabove described type including through-going electrically conductivefibres.

On the upper side surface of the double-sided printed circuit board 120,a circuit pad layout and circuit track layout is provided in accordancewith the teaching of the present invention providing electricalconnection to selected test points of the test surface 84. Below thelower side surface of the double-sided printed circuit board 120, andfurther below the sheet 124, a circuit board 126 is shown. The circuitboard 126 constitutes a thick-film circuit board having thick-filmlayers arranged on both side surfaces and through-platings providingconnections from the upper side surface of the thick-film circuit boardto the lower side surface thereof. The thick-film circuit board 126 isfixed in a fixation board 128 in which an aperture 130 of aconfiguration which is conform to the outer contour of the thick-filmcircuit board 126 is provided. Below the lower side surface of thethick-film circuit board 126, a second connector assembly according tothe invention is shown comprising a double-sided printed circuit board220 basically corresponding to the above double-sided printed circuitboard 120, and a first sheet 222 and a second sheet 224 corresponding tothe above sheets 122 and 124, respectively. Below the lower side surfaceof the double-sided printed circuit board 120, a further test head 100is shown defining an upwardly facing test surface 84.

Evidently, the provision of two connector assemblies according to theinvention and two test heads of the circuit board testing machineaccording to the invention sandwiching the circuit board such as thedouble-sided thick-film circuit board 126 therebetween as shown in FIG.9, renders it possible to carry out a test routine for testing both sidesurfaces of the circuit board and further through-going connections orthrough-platings of the circuit board to be tested. As mentioned above,the teaching of the present invention also renders it possible to testthe insulation between circuit pads or circuit tracks of either of thesides of the double-sided circuit board by providing access from a testpoint of one of the test surfaces to a selected area interposed thecircuit tracks or circuit pads of the circuit board to be tested throughone of the connector assemblies according to the invention.

As mentioned above, the test heads of the testing machine 70 arereciprocated in relation to each other so as to sandwich the connectorassemblies according to the invention having the circuit board to betested sandwiched therebetween

FIG. 10 shows a vertical sectional view through the top test head 100shown in the upper part of FIG. 9, the first connector assemblyaccording to the invention comprising the double-sided printed circuitboard 120 and the sheets 122 and 124, and further through the thick-filmcircuit board 126 to be tested and the sheet 224. Instead of thedouble-sided printed circuit board 220, the sheet 222 and the lower testhead 100, a short-circuiting or dummy circuit board 132 is arrangedbelow the sheet 224. The short-circuiting or dummy circuit board 132 isprovided with short-circuiting circuit tracks 134.

Whereas in FIG. 9 each circuit pad or circuit track or each areainterposed the circuit tracks or circuit pads and further thethrough-going connections of the circuit board may be tested indiviuallyfrom one side or from both sides of the circuit board, theshort-circuiting or dummy circuit bord 132 shown in FIG. 10 renders itpossible to test the circuit tracks or circuit pads of the one sidesurface of the circuit board, i.e. the thick-film circuit board 126 andfurther the circuit tracks or circuit pads of the opposite side surfaceof the thick-film circuit board and the through-going connections or thethrough-platings of the circuit board 126. It should, however, beemphasized that the one side access double-sided testing routine whichmay be carried out by employing the short-circuiting or dummy circuitboard 132 does not render it possible for all circuit board layouts todiscriminate between short-circuit connections of the circuit board,i.e. of the circuit board 126, and the short-circuiting connectionsprovided by the short-circuiting tracks 134 of the dummy orshort-circuiting circuit board 132. Therefore, the double-sideddouble-access testing routine shown in FIG. 9 is to be preferred formost applications, and particularly for applications involving highlycompact and highly delicate circuit track layouts of the circuit boardto be tested.

In FIG. 11, four test points 150, 152, 154 and 156 of a test surface ofthe above described test head are shown schematically. Apart from thesetest points, the test surface comprises the further test points of thetest point matrix configuration. The first test point 150 is connectedto the collector of a first PNP transistor 160 and to the collector of afirst NPN transistor 161. Similarly, the test points 152, 154 and 156are connected to the collectors of a second, a third, and a fourth PNPtransistor 162, 164 and 166, respectively, and to the collector of asecond, a third, and a fourth NPN transistor 163, 165 and 167,respectively. The test points 150 and 152 constitute test points of anidentical X-co-ordinate, i.e. test points which are connected to one andthe same of the circuit boards 106 shown in FIG. 8. Similarly, the testpoints 154 and 156 are test points of an identical X-co-ordinate,however of an X-co-ordinate different from the X-co-ordinate of the testpoints 150 and 152. As will be evident from description below, theY-co-ordinate of the first and third test points, i.e. the test points150 and 154 are identical to each other, and the Y-co-ordinate of thesecond and fourth test points, i.e. the test points 152 and 156 are alsoidentical to each other.

The bases of the first and second PNP transistors 160 and 162 areconnected to each other and the bases of further PNP transistors of thefurther test points of identical X-co-ordinate and further to a pin 170of a multi-pin plug designated X₁, which is a multi-pin plugcorresponding to the multi-pin plugs 116 shown in FIG. 8. Similarly, thebases of the first and second NPN transistors 161 and 163 are connectedto each other and to the bases of further NPN transistors of the furthertest points of identical X-co-ordinate and further to a pin 172 of amulti-pin plug X₂. The bases of the third and fourth PNP transistors 164and 166 are connected to each other and to the bases of the further PNPtransistors corresponding to the further test points of identicalX-co-ordinate and further to a pin 174 of the multi-pin plug X₁. Thebases of the third and fourth NPN transistors 165 and 167 are connectedto each other and to the bases of the further NPN transistorscorresponding to the test points of identical X-co-ordinate and furtherto a pin 176 of the multi-pin plug X₂.

The emitters of the first and third PNP transistors 160 and 164 whichcorrespond to the test points of identical Y-co-ordinate are connectedto each other and connected to the emitters of the PNP transistors ofthe further test points of identical Y-co-ordinate and further to a pin171 of a multi-pin plug designated Y₁. The emitters of the first andthird NPN transistors 161 and 165 which correspond to the test points ofidentical Y-co-ordinate are connected to each other and connected to theemitters of the PNP transistors of the test points of identicalY-co-ordinate and further to a pin 173 of a multi-pin plug designatedY₂. Similarly, the emitters of the second and third PNP transistors 162and 166 are connected to each other and connected to the emitters of thePNP transistors of the test points of identical Y-co-ordinate andfurther to a pin 175 of the multi-pin plug Y₁. Similarly, the emittersof the second and third NPN transistors 163 and 167 are connected toeach other and connected to the emitters of the PNP transistors of thetest points of identical Y-co-ordinate and further to a pin 177 of themulti-pin plug Y₂.

The switching and addressing transistor array shown in FIG. 11 functionsin the following manner: The PNP transistors, i.e. the transistors 160,162, 164 and 166 constitute transmit switches, whereas the NPNtransistors, i.e. the transistors 161, 163, 165 and 167 constitutereceive switches. If the test point 150 constitutes a current transmittest point, the pin 171 is switched high and a low base current is inputthrough the pin 170 to the base of the PNP transistor 160 whichconsequently supplies a high gain collector current to the test point150 the potential of which also switches high. The second transmitswitch 162 constituted by the second PNP transistor blocks as theemitter of the transistor is not switched high. The third and fourthtransmit switches constituted by the third and fourth PNP transistors164 and 166, respectively, also block as no base current are input tothe transistors through the pin 174. It should be emphasized that theaddressing a particular test point of co-ordinates X,Y is carried out byswitching the emitters of the transmit switches or the transmit PNPtransistors of the Y-co-ordinate in question high and by inputting a lowbase current into the bases of the transmit switches or PNP transistorsof the X-co-ordinate in question.

Similarly, the receive addressing is carried out by addressing anX-co-ordinate through the X₂ multi-pin plug, i.e. through the pin 172 orthe pin 176 shown in FIG. 11 and by sensing the voltages of the receiveswitches through the Y₂ multi-pin plug, i.e. through the pins 176 and177 shown in FIG. 11. It should be realized that as the voltage of thetransmit test point is switched high, a further test point electricallyconnected therewith is also switched high and the collector of thereceive switch or the receive NPN transistor connected to the furthertest point, e.g. the second NPN transistor 163 connected to the secondtest point 152 is also switched high. By inputting a low base currentthrough the pin 172 of the X₂ multi-pin plug, the NPN transistor 163starts conducting and switches its emitter high which is detectedthrough the pin 177. If the second test point 152 is not connected tothe transmit test point 150, the receive switch or receive NPNtransistor 163 does not switch its emitter high inspite of the input ofthe low base current through the pin 172. Obviously, the pin 173switches high due to the "receive" switch 161, but the pin 177 does notswitch high, and it is therefore easily detected that no connection isprovided between the test points 150 and 152. It should be emphasizedthat the addressing of the receive switches is carried out by inputtinga low base current into the receive NPN transistors, i.e. through thepins of the X₂ multi-pin plug and by detecting or sensing the voltagesof the emitters of the receive NPN transistors through the pins of theY₂ multi-pin plug.

As will be understood, the testing routine to be performed by addressingthe bases of the transmit and the receive transistors and by switchingthe collector of a single transmit transistor high and further bydetecting the voltages of the emitters of the receive transistors isvery easily carried out in an automatic testing machine by employing amicroprocessor or a similar controlling means. Obviously, thecontrolling means may be an external computer. However, in the presentlypreferred embodiment of the circuit board testing machine according tothe invention, a microprocessor is included in the circuit board testingmachine for controlling the above transmit and receive addressingroutines of the testing routine.

In FIG. 12, a block diagram of the presently preferred embodiment of thecircuit board testing machine is shown. As mentioned above, the circuitboard testing machine 70 comprises a microprocessor 180 which controlsthe overall operation of the apparatus and which consequently addressesthe transmit and receive switches as described above and which isoperated by means of the operator operable switches 80 and 81 anddisplays information to the operator by means of the display 82. Themicroprocessor 180 preferably further communicates through aninput/outport port with an external computer such as a minicomputer 182shown in FIG. 12. The minicomputer 182 comprises a terminal keyboard 183and a display 184 and communicates with a store 186 and further with aprinter 188. In the set-up shown in FIG. 12, the microprocessor of thecircuit board testing machine 70 according to the invention furthercommunicates with a sorter 190. The circuit boards which have beentested by means of the circuit testing machine are transferred, e.g. bymeans of a conveyor, to the sorter 190 which is addressed from themicroprocessor 180 of the testing machine for transferring the circuitboard into the cathegory to which it belongs. On the basis of the testroutines carried out under the control of the microprocessor 180, it ispossible to determine not only whether the circuit board is a correctcircuit board, but also--if certain deficiencies have been detected--todetermine what to do with the circuit board, i.e. to have it repaired ordiscarded. These alternatives are illustrated by a box 192 in the lowerleft-hand side of FIG. 12.

The provision of a microprocessor 180 for controlling the overalloperation of the circuit board testing machine 70 renders it possiblenot only to carry out the above addressing and testing routinescontrolled by the apparatus itself, but also to provide a "selflearning" circuit board testing machine. As will be appreciated, thecircuit board testing machine has to learn which of the test points ofthe test surfaces of the testing machine are connected to each other andwhich test points are not connected to other test points of the testsurfaces. In a first operational mode of the apparatus and consequentlyin a first operational mode of the microprocessor 180, a correct circuitboard is so to speak tested by the testing machine. The correct circuitboard is arranged sandwiched between the connector assemblies accordingto the invention and further sandwiched between the test heads of thecircuit board testing machine according to the invention, and byaddressing the individual test points of the two test heads themicroprocessor of the testing machine learns which test points areconnected to each other and which test points are not connected to othertest points. This information is stored in the microprocessor and mayfurther or alternatively be stored in the external store 186 of thecomputer 182 for later use. In addition to the self learning routine anoperator may through the external computer 182 define certain testpoints, e.g. test points corresponding to high insulation areas betweencircuit tracks or circuit pads of the circuit boards to be tested.

Although the invention has been described with reference to differentembodiments, it is to be understood that numerous amendments are obviousto the skilled art worker within the scope of the present invention asdefined in the appending claims.

I claim:
 1. A method of testing a circuit board by means of a circuitboard testing machine having a test surface including a number of testpoints electrically insulated relative to one another and arranged in amatrix configuration and for testing a circuit board of an electricallyinsulating material having circuit tracks of an eletrically conductivematerial arranged on at least a first side surface thereof, the methodcomprising:providing a connector assembly adapted to provide electricalconnection between selected areas of said first side surface of thecircuit board and selected test points of the test surface of thetesting machine, and wherein said connector assembly comprising:a boardof an electrically insulating material having opposite first and secondside surfaces, a first plurality of individual connector pads beingarranged on the first side surface of the connector assembly board in aconfiguration corresponding to said selected areas of said first sidesurface of the circuit board, a second plurality of individual connectorpads being arranged on the second side surface of the connector assemblyboard in a configuration corresponding to said selected test points ofsaid test surface of the testing machine, electrical cconductor meansextending through the board of the connector assembly board andelectrically connecting said individual connector pads of said firstplurality to respective individual connector pads of said secondplurality, and connector contact means secured to each of said connectorpads of said first plurality and of said second plurality, arrangingsaid first side surface of the circuit board facing said test surface ofthe testing machine, arranging said connector assembly so as to have itsfirst side surface face said first side surface of the circuit board andso as to have its second side surface face said test surface of saidtesting machine, and sandwiching said connector assembly between saidfirst side surface of the circuit board and said test surface of thetesting machine so as to provide electrical connection between saidselected areas of said first side surface of the circuit board and saidselected test points of the test surface of the testing machine throughsaid connector contact means secured to said connector pads of saidfirst plurality, through said individual connector pads of said firstplurality, through said electrical conductor means, through saidindividual connector pads of said second plurality, and through saidsecond connector contact means secured to said connector pads of saidsecond plurality.
 2. A method according to claim 1, wherein saidconnector contact means comprises at least one sheet of an electricallyinsulating material, arranged on one side surface of the board of theconnector assembly and having through-going, electrically conductivepaths.
 3. A method according to claim 2, wherein said sheet is a polymersheet, and wherein the through-going, electrically conductive paths areconstituted by metal fibres of high electrical conductivity, of athickness of 2-100 μm, and of a density of 1-20 fibres per mm².
 4. Amethod according to claim 3, wherein the metal fibres are of a noblemetal.
 5. A method according to claim 2, wherein the connector contactmeans comprises a first and a second sheet of an electrically insulatingmaterial and having through-going, electrically conductive paths, themethod further comprising arranging said first sheet on the first sidesurface of the board of the connector assembly so as to establishelectrical connection between said selected areas of the circuit boardand said individual connector pads of said first plurality, andarranging said second sheet on the second side surface of the board ofthe connector assembly, so as to establish electrical connection betweensaid selected test points of the testing machine and said individualconnector pads of said second plurality.
 6. A method according to claim1, wherein the board of the connector assembly is constituted by a boardof a double-sided printed circuit board having a first and a second sidesurface, wherein said individual connector pads of said first pluralityand of said second plurality comprise printed circuit pads arranged onsaid first side surface and on said second side surface, respectively,of the double-sided printed circuit board, and wherein said electricalconductor means are constituted by through-platings of said double sidedprinted circuit board.
 7. A method according to claim 6, wherein theboard of the double-sided printed circuit board is a 1.5 mm glass fibrereinforced epoxy resin board, and wherein the printed circuit pads are25-100 μm Cu-layer pads, provided with gold platings.
 8. A methodaccording to claim 7, wherein the individual connector means of saidfirst or second plurality further comprise connector bodies of anelectrically conductive material.
 9. A method according to claim 8,wherein the connector bodies are arranged in respective bores of asupporting board of an electrically insulating material and alignedrelative to their respective printed circuit pads.
 10. A methodaccording to claim 9, wherein the connector bodies are solid bodies ofan electrically conductive elastomer.
 11. A method according to claim 9,wherein the connector bodies are solid, metallic bodies.
 12. A methodaccording to claim 1, wherein the board of the connector assembly isconstituted by a thick-film substrate, and wherein said first and secondplurality of individual connector pads comprise layers provided inthick-film technique and arranged on a first side surface and on asecond side surface, respectively, of the substrate.
 13. A methodaccording to claim 1, wherein the board of the connector assembly isconstituted by a thin-film substrate, and wherein said first and secondplurality of individual connector pads comprise layers provided inthin-film technique and arranged on a first side surface and on a secondside surface, respectively, of the substrate.
 14. A method according toclaim 1, wherein the number of individual connector pads of said secondplurality is identical to that of said first plurality.
 15. A methodaccording to claim 1 and of testing a circuit board further havingcircuit tracks arranged on a second side surface opposite to said firstside surface, the circuit board testing machine having a further testsurface opposite to said at least one test surface, said further testsurface including a number of test points electrically insulatedrelative to one another and arranged in a matrix configuration, themethod further comprising:providing a further connector assembly adaptedto provide electrical connection between selected areas of said secondside surface of the circuit board and selected test points of saidfurther test surface of the testing machine, and said further connectorassembly comprising:a board of an electrically insulating materialhaving opposite first and second side surfaces, a first plurality ofindividual connector pads being arranged on the first side surface ofthe connector assembly board in a configuration corresponding to saidselected areas of said second side surface of the circuit board, asecond plurality of individual connector pads being arranged on thesecond side surface of the connector assembly board in a configurationcorresponding to said selected test points of said further test surfaceof the testing machine, electrical conductor means extending through theboard of the connector assembly board and electrically connecting saidindividual connector pads of said first plurality to respectiveindividual connector pads of said second plurality, and connectorcontact means secured to each of said connector pads of said firstplurality and of said second plurality, arranging said second sidesurface of the circuit board facing said further test surface of thetesting machine, arranging said further connector assembly so as to haveits first side surface face said second side surface of the circuitboard and so as to have its second side surface face said further testsurface of said testing machine, and sandwiching said further connectorassembly between said second side surface of the circuit board and saidfurther test surface of the testing machine so as to provide electricalconnection between said selected areas of said second side surface ofthe circuit board and said selected test points of the test surface ofthe testing machine through said further connector assembly's connectorcontact means secured to said connector pads of said first plurality,through said further connector assembly's individual connector pads ofsaid first plurality, through said further connector assembly'selectrical conductor means, through said further connector assembly'sindividual connector pads of said second plurality, and through saidfurther connector assembly's second connector contact means secured tosaid connector pads of said second plurality.
 16. A method according toclaim 1 and of testing a circuit board further having circuit tracksarranged on a second side surface opposite to said first side surface,the method further comprising:providing a short-circuiting circuit boardadapted to provide electrical interconnection between selected areas ofsaid second side surface of the circuit board said short-circuitingcircuit board comprising:a board of an electrically insulating materialhaving opposite first and second side surfaces, a first plurality ofindividual connector pads being arranged on the first side surface ofthe short-circuiting circuit board in a configuration corresponding tosaid selected areas of said second side surface of the circuit board, asecond plurality of individual connector pads being arranged on thesecond side surface of the short-circuiting circuit board, electricalconductor means extending through the board on the short-circuitingcircuit board and electrically connecting said individual connector padsof said first plurality to respective individual connector pads of saidsecond plurality, short-circuiting tracks being arranged on the secondside surface of the short-circuiting circuit board interconnectingselected individual connector pads of said second pluralitycorresponding to said selected areas of said second side surface of thecircuit board, and connector contact means secured to each of saidconnector pads of said first plurality and of said second plurality,arranging said second side surface of the circuit board facing saidfurther test surface of the testing machine, arranging saidshort-circuiting circuit board so as to have its first side surface facesaid second side surface of the circuit board and so as to have itssecond side surface face said further test surface of said testingmachine, and sandwiching said short-circuiting circuit board betweensaid second side surface of the circuit board and said further testsurface of the testing machine so as to provide electricalinterconnection between said selected areas of said second side surfaceof the circuit board through said short-circuiting circuit board'sconnector contact means secured to said connector pads of said firstplurality, through said short-circuiting circuit board's individualconnector pads of said first plurality, through said short-circuitingboard's electrical conductor means, through said short-circuitingcircuit board's individual connector pads of said second plurality,through said short-circuiting circuit board's second connector contactmeans secured to said connector pads of said second plurality, andthrough said short-circuiting circuit board's short-circuiting tracks.17. A method according to claim 1, wherein one of said selected areasconstitutes a selected area of the circuit tracks of the circuit board.18. A method according to claim 1, wherein one of the said selectedareas constitutes a selected area interposed between circuit tracks ofthe circuit board.